But simple tactile feedback isn't enough for touch typists. That's because the feel of a real keyboard goes beyond the limited range of surface textures that haptics can provide. For example, a touch typist continuously realigns his fingers by sensing the edges of each key as he types. The gaps between the keys and the bumps on the J and F home keys let him find the correct position by feel.

"On a touch screen, you lose all of that surface feel," says Mike Levin, a vice president at haptics technology provider Pacinian Corp.

With the iPad's virtual keyboard on smooth glass, touch typing is well nigh impossible. Even with haptics technology, touch typists won't be able to feel a tactile ridge along the edge of virtual keys, as they would on physical keyboards. But Pacinian's pressure-sensitive haptics can provide a different sensation for the home keys to differentiate them from the other keys on the keyboard, Levin says.

Unfortunately, today Pacinian's technology can only do that for one position at a time: You can sense a different pulse for the J or the F position, but not for both at once. Pacinian is working on a solution for that.

Force sensing, surface deforming

A bigger problem is that on today's capacitive touch screens, which detect your fingers' electrical conductivity as you touch the screen, you can't touch the keyboard to orient your fingers without activating the keys. On a physical keyboard, you touch the keys to determine position and then press down on them to type. That's missing on touch screens, which can sense a touch, but not the force with which it is applied.

Pacinian is also working to improve that. "The stuff we're working on adds a force sensor to improve the experience," says Levin. In this way, a user could use touch to find a button and then increase pressure to select it.

If Pacinian can provide feedback for both home key positions and use force-sensing technology to allow users to orient their fingers without activating keys, a virtual keyboard might be good enough for hunt-and-peck typists. But it's still not going to be enough for high-speed touch typists who are accustomed to rolling along at 100 to 150 words per minute. "You don't have those surface features to locate your fingers on," Levin says. So users would still have to look at the keyboard as they adjust their finger positions.